v0.3.0

 v0.3.0 reintroduces an important feature. it is possible to fall back
 on a line of defaults instead of just one.

 as an example, you can do something like this:
   default = Fry::HStore.from_hash({'greeting' => 'hello'}, nil)
   store1  = Fry::HStore.from_hash({}, default)
   store2  = Fry::HStore.from_hash({}, store1)
   store2.greeting # => 'hello'